Solicitor General Elena Kagan speaks at the annual meeting of the 7th Circuit Bar Association and Judicial Conference on Monday, May 3, 2010 in Chicago. (AP Photo/David Banks)

Washington (AP) -
President Barack Obama on Monday nominated Solicitor General Elena Kagan to the Supreme Court, declaring she would demonstrate the same independence, integrity and passion for the law exhibited by retiring Justice John Paul Stevens.

If confirmed by the Senate, Kagan would become the third woman on the high court. At 50, she is relatively young for the lifetime post and could help shape the high court's decisions for decades.

The former Harvard Law School dean "is widely regarded as one of the nation's foremost legal minds," Obama said. He introduced her in the White House East Room as "my friend."

Kagan said she was "honored and humbled by this nomination." She called it "the honor of a lifetime."

"I look forward to working with the Senate and thank you, Mr. President, for this honor of a lifetime."

Obama cited what he called Kagan's "openness to a broad array of viewpoints" and her "fair mindedness."

In a statement issued before Kagan had completed her remarks, the lawmaker who will preside over her confirmation hearing, Democratic Sen. Patrick Leahy of Vermont, said, "The Senate should confirm Ms. Kagan before" Labor Day.

"Our constituents deserve a civil and thoughtful debate on this nomination, followed by an up-or-down vote," he said.

The Republican leader, Sen. Mitch McConnell of Kentucky, said his party would make sure there was a "thorough process, not a rush to judgment" on the nomination.

"Judges must not be a rubber-stamp for any administration. Judges must not walk into court with a preconceived idea of who should win," he said, adding that Republicans would have a vigorous debate on that principle.

Obama began with high praise for the retiring Stevens, a leader of the court's liberals, calling him "a giant in the law," impartial and having respect for legal precedence.

Kagan "embodies the same excellence, independence and passion for the law," Obama said.

"She's an acclaimed legal scholar with a rich understanding of constitutional law. She is a former White House aide, with a lifelong commitment to public service and a firm grasp of the nexus and boundaries between our three branches of government," Obama said. Kagan served in the Clinton White House.

Obama noted that neither Kagan's mother nor father "lived to see this day, but I think her mother would relish this moment. I think she would relish, as I do, the prospect of three women taking their seat on the nation's highest court for the first time in history ... a court that would be more inclusive, more representative, more reflective of us as a people than ever before."

At 50 years old, Kagan would be the youngest justice on the court, which would give her the opportunity to extend Obama's legacy for a generation.